[Ohrrpgce] SVN: teeemcee/11711 Implement dithering for blending; global "blend algorithm" setting

[subversion at HamsterRepublic.com]

teeemcee
2020-04-08 18:47:11 -0700 (Wed, 08 Apr 2020)
213
Implement dithering for blending; global "blend algorithm" setting

There are three options (down from the 6+variants I actually implemented!)
The setting is editable in the slice editor.
Dithering is the default.
---
U   wip/blit.c
U   wip/const.bi
U   wip/ohrhelp/sliceedit.txt
U   wip/ohrhelp/sliceedit_game.txt
U   wip/sliceedit.bas
U   wip/slices.bas
U   wip/surface.bi
U   wip/surface.h
U   wip/whatsnew.txt